EP 0 798 451 B1 discloses a valve drive of an internal combustion engine with a camshaft, to which several cams, each of which actuates a gas exchange valve, are assigned. Each cam is supported nonrotatably on the camshaft but with the freedom to shift axially, wherein each cam comprises several cam faces arranged next to each other in the axial direction of the camshaft. Depending on the axial position of the cams on the camshaft, one of the cam faces of each cam is active and converts a rotational movement of the camshaft into stroking movements of a gas exchange valve. According to EP 0 798 451 B1, a stroke profile is formed on each of the two sides of each cam. An actuating pin cooperates with this profile to realize the axial displacement of each of the cams. By means of a stroke profile formed on the left side of a cam, the cam in question can be shifted axially to the left, and by means of a stroke profile formed on the right side of the cam, the cam in question can be shifted axially to the right. According to EP 0 798 451 B1, therefore, several stroke profiles and actuating pins are assigned to each cam to realize the ability to shift the cams along the camshaft.
A valve drive of an internal combustion engine, in which pairs of cams are combined into a cam piece so that they can be shifted jointly in the axial direction, is known from DE 101 48 178 A1. According to the prior art DE 101 48 178 A1, a stroke profile comprising intersecting stroke curves is assigned to the cam piece. An actuating pin cooperates with the stroke profile, which consists of two intersecting stroke curves, wherein, depending on which of the intersecting stroke curves of the stroke profile the actuating pin engages, the cam piece comprising several cams is shifted either axially to the left or axially to the right. By combining several cams into a cam piece, the number of stroke profiles can be reduced. Through the use of a stroke profile with intersecting stroke curves, the number of actuating pins required can be decreased.
When, in the case of the valve drive of DE 101 48 178 A1, an actuating pin travels through the area where the intersecting stroke curves intersect, the valve drive can malfunction, because there is the danger that the actuating pin can become jammed in the intersection area or, upon traveling through the intersection area, it can arrive in the area of the wrong stroke curve. This is disadvantageous. There is therefore a need for a valve drive by means of which such malfunctions can be reliably avoided and which at the same time makes it possible to reduce the number of actuating pins required.
Against this background, the present invention relates to the goal of creating a novel valve drive of an internal combustion engine. According to aspects to the invention, a first stroke curve and a second stroke curve of the stroke profile are contoured both in the axial direction of the stroke profile, i.e., of the camshaft, and also in the radial direction of the stroke profile, i.e., of the camshaft, in such a way that the contouring in the axial direction of the stroke profile, i.e., of the camshaft, is responsible for a defined axial displacement of the cam or cam piece in question, and the contouring in the radial direction of the stroke profile, i.e., of the camshaft, prevents the stroke curves from colliding. By means of the inventive valve drive, malfunctions can be reliably avoided while at the same time the number of actuating pins required can be reduced.
Preferred elaborations of the invention can be derived from the following description. Exemplary embodiments of the invention are explained on the basis of the drawing, but the invention is not to be considered limited to them.